Pressure amplifiers for downhole drilling tools

ABSTRACT

A drilling system includes a drill string having a BHA carrying a drill bit, a steering pad carried by the BHA and radially moveable relative to a longitudinal axis of the BHA and a pressure amplifier connected between the steering pad and a hydraulic fluid at a first pressure, the pressure amplifier comprising a piston axially moveable in response to application of the first hydraulic pressure to move the steering pad radially at a steering force.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/158,829, filed May 8, 2015, which is incorporated herein by reference in its entirety.

BACKGROUND

This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.

Oil and gas reservoirs may be accessed by drilling wellbores to enable production of hydrocarbon fluid, e.g. oil and/or gas, to a surface location. In many environments, directional drilling techniques have been employed to gain better access to the desired reservoirs by forming deviated wellbores as opposed to traditional vertical wellbores. However, forming deviated wellbore sections can be difficult and requires directional control over the orientation of the drill bit used to drill the deviated wellbore.

Rotary steerable drilling systems have been used to drill deviated wellbore sections while enabling control over the drilling directions. Such drilling systems often are classified as push-the-bit systems or point-the-bit systems and allow an operator to change the orientation of the drill bit and thus the direction of the wellbore.

SUMMARY

A steerable drilling tool includes a steering pad radially moveable relative to a longitudinal tool axis and a pressure amplifier operationally connected to the steering pad to increase a hydraulic fluid pump pressure applied to the steering pad. A method in accordance with aspects of a method includes applying a first hydraulic pressure to a pressure amplifier operationally connected to a steering pad located in a bottom hole assembly (BHA) having a drill bit and disposed in a wellbore, driving a piston of the pressure amplifier axially relative to a longitudinal axis of the BHA and moving the steering pad with a steering force radially away from the longitudinal axis of the BHA in response to driving the piston axially.

A drilling system includes a drill string having a BHA carrying a drill bit, a steering pad carried by the BHA and radially moveable relative to a longitudinal axis of the BHA and a pressure amplifier connected between the steering pad and a hydraulic fluid at a first pressure, the pressure amplifier comprising a piston axially moveable in response to application of the first hydraulic pressure to move the steering pad radially at a steering force.

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic view of an example of a drill string incorporating a steerable drilling system and pressure amplifier according to one or more aspects of the disclosure.

FIG. 2 illustrates an example of a steerable drilling tool incorporating a pressure amplifier according to one or more aspects of the disclosure.

FIG. 3 illustrates an example of another steerable drilling tool incorporating a pressure amplifier according to one or more aspects of the disclosure.

FIG. 4 illustrates a differential pressure amplifier incorporated for example in a steering actuator of a steerable drilling tool according to one or more aspects of the disclosure.

FIG. 5 illustrates a multiple stage pressure amplifier in a pressure amplification configuration incorporated for example in a steering actuator of a steerable drilling tool according to one or more aspects of the disclosure.

FIG. 6 a multiple stage pressure amplifier in a force amplification configuration incorporated for example in a steering actuator of a steerable drilling tool according to one or more aspects of the disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

As used herein, the terms connect, connection, connected, in connection with, and connecting may be used to mean in direct connection with or in connection with via one or more elements. Similarly, the terms couple, coupling, coupled, coupled together, and coupled with may be used to mean directly coupled together or coupled together via one or more elements. Terms such as up, down, top and bottom and other like terms indicating relative positions to a given point or element are may be utilized to more clearly describe some elements. Commonly, these terms relate to a reference point such as the surface from which drilling operations are initiated.

Referring generally to FIG. 1, an embodiment of a drilling system 20 in which pressure amplifiers 10 can be incorporated. System 20 includes a bottom hole assembly (BHA) 22 which is part of a drill string 24 used to form a directionally drilled wellbore 26. The illustrated bottom hole assembly 22 of drilling system 20 includes a steerable drilling assembly 28, e.g. a rotary steerable system, which controls the drilling orientation of a drill bit 30. The steerable drilling assembly 28 in FIG. 1 is illustrated as a point or hybrid type system including steerable system components 32, 34 which pivot with respect to each other to enable the desired directional drilling of wellbore 26. Steering actuators 36 may be mounted between components 32 and 34 to control the pivoting of component 34 with respect to component 32 by providing the desired lateral forces for steering the steerable drilling assembly 28 when forming the desired, deviated wellbore 26. The steerable system components 32, 34 may be coupled together by a pivot joint 38, such as a universal joint. The illustrated steerable drilling system is a non-limiting example of a steerable drilling system in which embodiments of this disclosure can be incorporated.

A control system generally identified with the numeral 40 selectively directs drilling fluid to the steering actuators 36 to extend the actuators radially or laterally relative to the drill string and into contact with the outer steerable component 34 (e.g., sleeve) or into contact with the wellbore wall to steer the drill bit 30. The control system 40 may include for example control electronics 42 and one or more valves 44 (e.g., spider valve, bistable valve, etc.). A pressure amplifier 10 is operationally, hydraulically and or physically, connected to each of the steering actuators 36 to multiple the pump pressure that is applied to the steering actuator. The steering actuator can be provided in various forms including steering pistons or balls having an outer profile or pad to contact the steering sleeve or wellbore wall, the steering actuator can include a hinged member that pivots relative to the tool to extend radially or laterally outward. Non-limiting examples of steerable systems in which the pressure amplifier can be utilized are disclosed in U.S. Pat. Nos. 8,590,636, 8,701,795, 8,708,064, 8,763,725 and 9,057,223 the teachings of which are incorporated herein by reference.

Depending on the environment and the operational parameters of the drilling job, drilling system 20 may comprise a variety of other features. For example, drill string 24 may include drill collars 46 which, in turn, may be designed to incorporate desired drilling modules, such as logging-while-drilling and/or measurement-while-drilling modules 48. In some applications, stabilizers may be used along the drill string to stabilize the drill string with respect to the surrounding wellbore wall. Various surface systems also may form a part of the drilling system 20. In the example illustrated, a drilling rig 50 is positioned above the wellbore 26 and a drilling mud system 52 is used in cooperation with the drilling rig. For example, the drilling mud system 52 may be positioned to deliver drilling fluid 54 from a drilling fluid tank 56. The drilling fluid 54 is pumped (pump 53) through appropriate tubing 58 and delivered down through drilling rig 50, into drill string 24, and down through drill bit 30. In many applications, the return flow of drilling fluid flows back up to the surface through an annulus 60 between the drill string 24 and the surrounding wellbore wall (see arrows 62 showing flow down through drill string 24 and up through annulus 60). The drilling system 20 also may comprise a surface control system 64 which may be used to communicate with steerable drilling assembly 28. In some embodiments, the surface control system 64 communicates with a downhole steering control system within steerable drilling assembly 28.

FIG. 2 schematically illustrates a non-liming example of a steerable drilling assembly 28 incorporating a pressure amplifier 10. With additional reference to FIG. 1, the illustrated steerable drilling assembly 28 is in the form of a rotary steerable system which utilizes steering actuators 36 to control the relative angular orientation between steering components 32 and 34. The steering components 32 and 34 are pivotally coupled to each other via pivot joint 38 which, in this particular example, is in the form of a universal joint. Downhole drilling tools generally utilized the pumping pressure (pump 53), of the drilling fluid 54 to control the steering actuator 36. The drilling fluid is directed for example by the downhole steering control system 40, through a control valve 44 to the steering actuator 36. The applied drilling fluid pressure actuates the steering actuator (e.g., piston, ball) radially outward relative to the longitudinal axis 66 of the tool (e.g., BHA). In the example of FIG. 2, the actuator 36 (e.g. piston body) extends radially outward to pivot the steering components 32, 34 relative to one another. In some drilling tools, the pads are extended radially from the drilling tool to contact the wall of borehole (e.g. a push-type), for example as illustrated in FIG. 3. The pump pressure can be utilized to operate different features of the downhole system and the various mechanism of the bottom hole assembly are not rated at the same pressure. If the pump pressure is increased over certain limits the bottom hole assembly parts may fail, for example sensors, seals, and metal deformation and erosion. Pressure amplifiers 10 are disclosed herein which facilitate applying a hydraulic pressure greater than that of a drilling fluid pump pressure. In the example of FIG. 2, each actuator 36 is connected with a respective fluid pressure amplifier 10.

FIG. 3 schematically illustrates another non-liming example of a steerable drilling assembly 28 incorporating a pressure amplifier 10. The illustrated bottom hole assembly 22 includes a drill collar 46 having steering actuators 36 associated therewith, each steering actuator 36 moveable to move an associated pad 37 between an extended, radially outward position and a retracted position. The pad 37 may be an outer portion of the steering actuator 36 or a separate member moveable with and by the actuator 36. The bottom hole assembly 22 may include a drilling motor 68 carried by the drill string 24 that may be utilized for example to rotate drill bit 30 and the drill collar 46 carrying steering actuators 36.

The steering actuators 36 (e.g., pistons, balls) are moved from retracted positions toward extended positions by supplying the drilling fluid, under pressure, to the cylinders 70 associated therewith, return movement occurring as the drilling fluid is able to escape from the cylinders through an exhaust 72. The supply of fluid to the cylinders 70 from a fluid conduit 74 via pressure amplifiers 10 is controlled by control valves 44. The operation of control valves 44 are controlled for example by controller 42 using information from, for example, inclination and azimuth sensors 76. The control valves, controller and sensors may be electrically powered from a power source 78 such as a load cell or battery.

To achieve steering of the drilling direction, the controller 42 controls the valves 44 so as to determine which of the steering actuators 36 is in the extended position. By extending the steering actuator and pad 37 into engagement with the wellbore wall a laterally acting reaction force is applied to the collar 46 and hence to the drill bit 30. By moving the steering actuator as the collar rotates the reaction force can be applied in a substantially constant direction resulting in the formation of curve or dogleg in the borehole.

FIG. 4 illustrates a pressure amplifier, generally denoted by the numeral 10, in operational connection with a steering actuator 36 and deployed in steerable drilling assembly 26 and a bottom hole assembly 22. In this example, the pressure amplifier is hydraulically connected to the steering actuator 36. The pressure amplifier 10 in FIG. 4 is a differential pressure amplifier. With additional reference to FIGS. 1-3, drilling fluid 54 at about pump pressure is routed, for example by a downhole control system 40, from fluid passage or conduit 74 through a control valve into an inlet 80 of the pressure amplifier 10, at a first pressure identified as the pump pressure. The first pressure acts on an input piston area 82 of an amplifier piston 84 which transfers the pressure to an amplifier fluid 86 in contact with the outlet piston area 88 of the piston. The input piston area 82 is greater than the output piston area 88 and the ratio of the input piston area to the output piston area is the pressure amplification coefficient. The amplifier fluid 86 is in contact with the output piston area 88 and is supercharged (the input pressure multiplied by the pressure amplification coefficient) and applied to the actuator surface area 90 of the steering actuator 36. This will move the steering actuator 36 at a steering piston force 92 as illustrated in FIG. 4 radial or lateral to the longitudinal axis of the bottom hole assembly 22. This steering piston force 92 is the force applied to bias the drill bit.

In the example of FIG. 4 the amplifier piston 84 is disposed in a cylinder 85 which may extend for example axially relative to the BHA such that that piston 84 travels axially, e.g. along the longitudinal axis 66 (FIG. 2) of the BHA. In accordance to aspects of the disclosure the pressure amplifier 10 facilitates applying a higher hydraulic fluid to the steering actuator than can be provided by the pump 53 (FIG. 1). For example, increasing the pump pressure may result in surpassing the pressure rating of other tools in the drilling string or result in excessive drilling pressures.

FIG. 5 illustrates an example of a multiple stage pressure amplifier 10 in a pressure amplification configuration deployed in steerable drilling assembly 26 and a bottom hole assembly 22. In this example, the pressure amplifier 10 has an amplifier piston or shaft 84 moveably disposed in a cylinder 85 and having a first input piston surface area 82 and a second input piston surface area 83 for each additional stage of the amplifier. In this example the pressure amplifier 10 has three stages. The output surface area 88 acting on the charging fluid 86 has a surface area substantially equal to the first input area 82. In this example the amplifier pressurizes the charging fluid 86 (P_(CF)) according to the following:

$\begin{matrix} {\mspace{79mu} {{P_{CF} = {P_{Inlet}\left\lbrack {1 + {\left( {X\text{?}1} \right)\frac{A_{83}}{A_{88}}}} \right\rbrack}}{\text{?}\text{indicates text missing or illegible when filed}}}} & (1) \end{matrix}$

where P_(Inlet) is the inlet pressure of fluid 54, e.g., pump pressure, X is the number of stages, A₈₃ is the area of the second input surfaces and A₈₈ is the area of the output surface area.

The pressure improvement over the pump pressure (inlet pressure) is:

$\begin{matrix} {\mspace{79mu} {{P_{imp} = {\left( {X\text{?}1} \right)\left( \frac{P_{Inlet} \times A_{83}}{A_{88}} \right)}}{\text{?}\text{indicates text missing or illegible when filed}}}} & (2) \end{matrix}$

With reference to FIG. 5, the multiple stage pressure amplifier 10 is in fluidic connection with a steering actuator pad. When the pump, e.g., pump 53 in FIG. 1, is operating within a safe pressure zone, the hydraulic pressure applied to the steering pad, and thus the steering force, can be increased over that provided by the pump pressure.

FIG. 6 schematically illustrates a multistage pressure amplifier 10 utilized in the force amplification configuration and deployed in a bottom hole assembly 22 to radially actuate a pad 37 (e.g., rocker assembly) of a steerable drilling tool 28. In the force configuration the amplifier 10 is arranged in a similar fashion as in the pressure configuration illustrated in FIG. 5 however the amplifier shaft or piston 84 is physically connected to the steering actuator 36. A mechanical linkage 94 converts the axial movement of the amplifier shaft 84 and in this example the steering actuator 36 into a radial movement of the pad 37 relative to the axis 66. In the example, the steering or piston force 92 is the axial force applied to shaft 84. For a single stage force amplifier the piston force 92 is equal to the inlet pressure 80, i.e. the pump pressure, time the inlet piston area 82. With multiple stages the force is increased by the inlet pressure applied to the second input surface area 83 of the respective stage. The force improvement (F_(imp)) to the steering piston force 92 over utilizing the inlet pressure without the pressure amplifier 10 in FIG. 6 is:

$\begin{matrix} {\mspace{79mu} {{F_{imp} = {\left( {X\text{?}1} \right)\left( {P_{inlet} \times A_{83}} \right)}}{\text{?}\text{indicates text missing or illegible when filed}}}} & (1) \end{matrix}$

The amplifier shaft 84 and cylinder 85 are oriented axially, i.e. along longitudinal axis 66 of the tool, to accommodate the space limitations in a downhole tool. In the example of FIG. 6, the amplifier piston cylinder 85 and the steering actuator 36 cylinder portion 70 are oriented in the axial direction with the piston movement and the piston push in the axial direction. The piston cylinder 70, 85 is longer and the movement of the piston (actuator 36 and amplifier 84) is longer than that permitted in a radial piston arrangement. The longer axial movement allows for more radial lifting movement of the steering pad (e.g., rocker assembly). During operation, the pad 37 or other components wear and/or become washed out requiring that the pad move further radially than prior to the wear. The axial piston assembly and pressure amplifier facilitates the additional radial movement needed for the pad without compromising the piston seal, e.g. the piston seal being pushed out of the cylinder.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, features shown in individual embodiments referred to above may be used together in combinations other than those which have been shown and described specifically. Accordingly, any such modification is intended to be included within the scope of this disclosure. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not just structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke means-plus-function for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. 

What is claimed is:
 1. A steerable drilling tool, comprising: a steering pad radially moveable relative to a longitudinal tool axis; and a pressure amplifier operationally connected to the steering pad to increase a hydraulic fluid pump pressure applied to the steering pad.
 2. The tool of claim 1, wherein the pressure amplifier comprises a piston configured to move along an axial path substantially parallel to the tool axis.
 3. The tool of claim 1, wherein the pressure amplifier is a differential pressure amplifier.
 4. The tool of claim 1, wherein the pressure amplifier is a multiple stage pressure amplifier.
 5. The tool of claim 1, wherein the pressure amplifier is configured to act on a fluid to radially move the steering pad.
 6. The tool of claim 1, wherein the pressure amplifier is configured to act on a shaft to radially move the steering pad.
 7. The tool of claim 1, wherein the tool comprises a first component pivotally connected to a second component carrying a drill bit, the first and the second component pivot relative to one another in response to radially extending the steering pad.
 8. The tool of claim 7, wherein the pressure amplifier comprises a piston configured to move along an axial path substantially parallel to the tool axis, and the piston is configured to act on a fluid to radially move the steering pad.
 9. The tool of claim 7, wherein the pressure amplifier comprises a piston configured to move along an axial path substantially parallel to the tool axis, and the piston is configured to act on a shaft to radially move the steering pad.
 10. A method, comprising: applying a first hydraulic pressure to a pressure amplifier operationally connected to a steering pad located in a bottom hole assembly (BHA) having a drill bit and disposed in a wellbore; driving a piston of the pressure amplifier axially relative to a longitudinal axis of the BHA; and moving the steering pad with a steering force radially away from the longitudinal axis of the BHA in response to driving the piston axially.
 11. The method of claim 10, wherein the pressure amplifier is a differential pressure amplifier.
 12. The method of claim 10, wherein the pressure amplifier is a multiple stage pressure amplifier.
 13. The method of claim 10, wherein the moving the steering pad comprises increasing a pressure of a charging fluid over the first hydraulic pressure in response to driving the piston axially, the piston operationally connected to the steering pad by the charging fluid.
 14. The method of claim 10, wherein the piston of the pressure amplifier is operationally connected to the steering pad by a shaft.
 15. The method of claim 10, further comprising applying the steering force via the pad to a wall of the wellbore.
 16. The method of claim 10, further comprising pivoting first component and a second component of the BHA relative to one another in response to radially extending the steering pad.
 17. A drilling system, comprising: a drill string having a bottom hole assembly (BHA) carrying a drill bit; a steering pad carried by the BHA and radially moveable relative to a longitudinal axis of the BHA; and a pressure amplifier connected between the steering pad and a hydraulic fluid at a first pressure, the pressure amplifier comprising a piston axially moveable in response to application of the first hydraulic pressure to move the steering pad radially at a steering force.
 18. The system of claim 17, wherein the pressure amplifier is one of a differential pressure amplifier and a multiple stage pressure amplifier.
 19. The system of claim 17, wherein the piston is configured to act on a fluid to radially move the steering pad.
 20. The system of claim 17, wherein the piston is configured to act on a shaft to radially move the steering pad. 